ESTIMATION OF EARTHQUAKE-INDUCED SETTLEMENT OF ROCKFILL DAMS

Because there are frequent large earthquakes in Japan, it is very important to evaluate the seismic safety of dams against large earthquake motion. On March 30, 2005, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of the Japanese Government issued the "Guidelines for Seismic Performance Evaluation of Dams During Large Earthquakes (Draft)" (hereinafter referred to as the "Guidelines") to organizations including all Regional Bureaus of the MLIT. This document systematically describes methods of evaluating the seismic safety of dams subjected to large-scale earthquakes. According to the "Guidelines," the seismic safety of rockfill dams should be evaluated based on the amount of sliding displacement resulting from large earthquake motion. But, during the Mid-Niigata Earthquake in 2004, a large settlement with no sliding was observed at a rockfill dam at which consolidation settlement had almost finished before the earthquake. Thus, to accurately estimate settlement due to large earthquake motion, the settlement should be reproduced by some other method, such as a deformation analysis based on cumulative damage theory. In this study, we calculated the sliding deformation and settlement based on cumulative damage theory in the case of an earth core rockfill dam (ECRD) and a concrete face rockfill dam (CFRD), under various conditions. This confirmed that the deformation pattern of an actual dam due to large earthquakes could qualitatively be reproduced by deformation analysis method based on cumulative damage theory.